Conventionally, as a method for preventing a printed matter from being copied illegally by copy machines, there is a way of printing in the printed matter a pattern having a high resolution more than that by the resolving powers of the copy machines. However, in recent years, capabilities of the copy machines have been enhanced dramatically, so that the resolving powers of the copy machines are increased, and thus, by such a way, it becomes difficult to prevent a printed matter from being copied illegally.
In this respect, for example in Patent Document 1, as a method for making it unable by the copy machines to reproduce a feature of the printed matter, there is disclosed a way in which a print paper formed with a concavity-convexity forming layer that causes volume increase by heat treatment, is used so that concavities and convexities are developed on a printed image, and a copied matter is identified depending on whether the concavities and convexities with a predetermined pattern emerge or not. Further, for example in Patent Document 2, there is disclosed a method in which a hologram is provided on a printed matter and authenticity determination of the printed matter is made depending on whether or not there is a match between identification information and that from the hologram.